The present invention relates to mechanical pencils and more particularly to a mechanical pencil of the type having a lead-feeding device operable by forward shake of the pencil to feed or project a pencil lead by a specific distance out through the writing end of the pencil.
The mechanical pencils of the above stated type are disclosed in U.S. Pat. No. 4,205,924 to Sumita and comprise a pen barrel, a lead gripping chuck provided within the pen barrel adjacent to the forward end thereof, a lead reservoir fixed to the rear end of the chuck for storing leads to be fed into the chuck, and a weight provided in the pen barrel so as to be movable forwardly and rearwardly along the lead reservoir. The weight is adapted to impart its inertia force to the chuck, upon being given a forward shake, to feed the chuck and the lead forward. A slider is disposed in the rear end of the pen barrel for forward and rearward shifting movement relative to the pen barrel. The slider is adapted to impart a forward stroke to the lead reservoir and hence the chuck. A knob is provided on the slider.
In the mechanical pencils of the above stated character, whenever the weight within the pen barrel is subjected to a forward shake, the weight causes the lead held by the chuck to be fed forward so as to project out through the writing end of the pencil barrel. Such forward shake occurs when the pencil is being carried by the owner of the pencil. As a results, the lead is unintendedly fed out of the writing end of the pencil while being carried by the owner.
In order to prevent such a phenomenon from occuring, a mechanism for preventing feeding-out of the lead was proposed. The mechanism comprises an operating member projecting through an engaging slot formed in the pen barrel. The operating member is capable of being locked or unlocked relative to the pen barrel. When the operating member is locked with respect to the pen barrel, the lead gripping chuck is prevented from advancing forward so that the lead will not be fed forward.
With the mechanism described above, it is troublesome to manipulate the operating member for locking and unlocking it relative to the pen barrel. Furthermore, the mechanism has a complicated construction for preventing forward movement of the chuck when the operating member is locked relative to the pen barrel. The mechanism has further various practical problems to be solved.